If you think that small changes in your habits—like walking an extra mile a day—will make a big difference in your weight or that crash diets rarely keep pounds off over the long term, you’ve fallen for two myths that even fool scientists, according to a startling new paper in The New England Journal of Medicine.
In fact, almost everything you think you know about weight loss is wrong—and unscientific notions about how to get pounds off are so pervasive that even doctors and scientists believe them, the researchers report.
Indeed, there are more myths about obesity than there are in any other field of medicine, Dr. Jeffrey Friedman, a Rockefeller University obesity researcher, told the New York Times. And these fallacies are making us fat.
Here’s a look at surprising myths about weight loss—plus the scientific facts-—presented in the NEJM paper.
Fact: A diet that’s high in fruits and vegetables has many health benefits, including lower risk for heart attacks and strokes. However, this habit alone isn’t enough to whittle off weight unless you also make other changes in your behavior, such as exercising more and cutting down on sweets. Otherwise, you could even gain weight on a diet that’s high in fruits and vegetables.
Fact: Eating a healthy breakfast is often recommended as part of a balanced diet and because it helps rev your metabolism, but two randomized controlled studies (the scientific gold standard of scientific research) comparing people who were assigned to eat breakfast or skip their morning meal found no differences in weight loss.
Fact: While crash diets can indeed be bad for your health if you eat an unbalanced diet (such as only consuming cabbage soup), within weight-loss studies, dropping pounds fast has actually been linked to greater sustained weight loss down the road. A number of studies have shown that very low-calorie diets can be highly effective, compared to ones in which weight is shed more gradually. Therefore for people who are obese, say the study authors, a recommendation to lose weight slowly might actually undermine success.
Fact: School physical education classes, in their current form, have not been shown to reduce or prevent obesity. Three studies focused on analyzing the impact of expanding the amount of time kids spend in gym classes found inconsistent effects on the kids’ body mass indices. Two analyses of previous research also reported that even specialized school-based programs to promote exercise were ineffective at combatting obesity. This may be because gym classes don’t offer workouts that are long, intense, and frequent enough to make a difference. It’s crucial for kids to be physically active after school and to limit TV time, junk food, and sugary beverages.
Fact: This unscientific notion is even found in national health guidelines. An example of this concept is that if you burn an extra 100 calories a day by walking a mile, you will supposedly lose more than 50 pounds over a 5-year period. Actually, you’d only lose about 10 pounds because your body adapts to the change and your calorie requirements drop. Small changes are a good way to start, but their results have been over-promised.
Fact: You’ve probably seen calculations saying that sex torches up to 300 calories. Yet the only study that actually measured the energy output reported that sex only lasted an average of six minutes and burned just 21 calories. “Disappointing, isn’t it?” says lead study author David Allison, Ph.D., director of the Nutrition Obesity Research Center at the University of Alabama at Birmingham.
Fact: Although observational studies, in which people are tracked over a number of years, do show that people whose weight bounces up and down tend to die at a younger age than those who maintain a steady weight, this type of study isn’t designed to prove a cause-and-effect relationship. It’s also possible that weight swings could be linked to changes in the person’s health. For example, someone with cancer is likely to lose weight while undergoing chemotherapy, or medications for some diseases can cause weight gain. Therefore, this belief remains unproven.
Fact: A study of more than 13,000 kids who were tracked for more than six years found no support for this belief. However, breastfeeding has many other health benefits for babies and should be encouraged, the researchers note.
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